首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   295篇
  免费   18篇
林业   14篇
农学   16篇
基础科学   2篇
  45篇
综合类   13篇
农作物   82篇
水产渔业   23篇
畜牧兽医   101篇
园艺   2篇
植物保护   15篇
  2022年   4篇
  2021年   12篇
  2020年   7篇
  2019年   12篇
  2018年   13篇
  2017年   6篇
  2016年   10篇
  2015年   16篇
  2014年   16篇
  2013年   26篇
  2012年   26篇
  2011年   23篇
  2010年   14篇
  2009年   11篇
  2008年   22篇
  2007年   21篇
  2006年   9篇
  2005年   10篇
  2004年   17篇
  2003年   12篇
  2002年   6篇
  2001年   5篇
  2000年   13篇
  1999年   1篇
  1985年   1篇
排序方式: 共有313条查询结果,搜索用时 0 毫秒
101.
This paper suggests the optimal conditions to prevent electrostatic charge in the laundry by the evaluation of the electrostatic characteristics during the drying process. Cotton, nylon, and polyester fabrics were used as test specimens, employing the standard washing cycle. The electrostatic characteristics of the laundry were measured after the automatic drying process. This paper investigates the optimal conditions for preventing electrostatic charges in laundry by evaluating the electrostatic characteristics that occur during the drying process. Cotton, nylon, and polyester fabrics were used as the test specimens, employing a standard washing cycle. The electrostatic characteristics of the laundry were measured immediately after the automatic drying process. The results, showed that the moisture content decreased and the electrostatic charge increased with drying time. The specimen fabrics had already dried up before completion of the standard drying cycle. Consequently, the excessive drying generated an electrostatic charge due to removal of the traces of remaining moisture and the resulting excessive friction. For cotton fabrics, the electrostatic charge was under 1000 V even for the maximum drying time due to the intrinsic high moisture regain of cotton. On the other hand, the electrostatic charge produced for nylon fabrics increased rapidly with the drying time, and amounted up to approximately 8000V after 120 minutes. The results also indicated that the electrostatic charge could be decreased by drying fabrics of only one kind. When mixed kinds of fabrics were dried, the electrostatic charge increased remarkably. Therefore, it is suggested that laundry be classified and washed according to the kinds of fiber, and not be dried excessively to reduce electrostatic charge. In addition, the proper use of a softener is effective in reducing the electrostatic charge.  相似文献   
102.
Mechanical properties of wool fiber in the stretch breaking process   总被引:1,自引:0,他引:1  
Short wool fibers obtained by the stretch breaking process can be blended with cotton fibers and processed in a cotton spinning system, which has a high production rate. For the structural property of the wool fiber after stretch breaking, the diameter and length of the wool fiber were measured as a function of time. The diameter of the broken fibers was finer than the diameter of untreated fibers. The fiber diameter at the break point was the finest and was more irregular than the original fiber. The broken fiber showed mechanical properties of increased modulus, decreased breaking strain, and increased breaking strength.  相似文献   
103.
Thermal properties of copolyetherester/silica nanocomposites were examined by using DSC and TGA. The segmented block copolyetheresters with various hard segment structures and hard segment contents (HSC) were synthesized and their silica nanocomposite films were prepared by solution casting method. The nano-sized fumed silica particles were found to act as a nucleating agent of the copolyetheresters. The nanocomposites always showed reduced degree of supercooling or faster crystallization than the corresponding copolyetheresters. The nanocomposites also showed increased hard segment crystallinity except HSC 35 sample which had short hard segment length. In case of 2GT [poly(ethylene terephthalate)] copolyetheresters, which were not developed commercially because of their low crystallization rate, the hard segment crystallinity increased considerably. The copolyetherester/silica nanocomposites showed better thermal stability than copolyetheresters.  相似文献   
104.
Waterproof fabrics are seamed and sealed by waterproof sealing tape to prevent water from penetrating through the stitch holes. As this process may change the mechanical properties of breathable waterproof fabric related to its deformation with human body, the changes in mechanical properties were investigated. In both of parallel and perpendicular directions, tensile characteristics were remarkably changed with seaming and sealing processes. The increase of LT and WT means that the clothing sealed by waterproofing tape may produce somewhat discomfort feeling. On the other hand, the bridge of the sewing thread seemed to be reinforced by waterproofing tape. Shear characteristics such as G, 2HG, and 2HG5 gradually increased with seaming and sealing processes in parallel direction. However, they decreased with sealing process in perpendicular direction because the seam line work as an axis located at the center of the testing range.  相似文献   
105.
ABSTRACT

Nutrient uptake over a 72 h culture period by clonal micropropagules of Phalaenopsis Tanigawa × Yukimai Dream ‘KS 370’ and ‘KS 352’ were surveyed by Ichihashi's (1997) Ichihashi, S. 1997. “Orchid production and research in Japan”. In Orchid Biology, Reviews and Prospectives, Edited by: Arditti, J. and Pridgeon, A. M. 171212. Dordrecht, , The Netherlands: Kluwer.  [Google Scholar] nutrient solution at the original ion strength and its half and quarter. Uptake of major anions [nitrate (NO3 ?), phosphate (H2PO4 ?), and sulfate (SO4 2?)] and cations [ammonium (NH4 +), potassium (K+), calcium (Ca2+), and magnesium (Mg2+)] measured with an ion chromatograph increased as the ionic strength of the solution increased in both cultivars. The final uptake rates of nutrients were 0.8, 2.0, 2.1, 1.2, 3.0, 2.0, and 1.6 me L?1, respectively in the order of ions mentioned above. The ratios of the uptake rates between cations (mono or bivalent) were almost in proportion to the ratio of their initial ion strength. Therefore, no antagonistical absorption of cations was found in that ion strength. Leaf content of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and copper (Cu) increased as the ionic strength of the solution increased, but concentrations of iron (Fe), manganese (Mn), and zinc (Zn) were not affected significantly. Nitrogen (N) content of leaves in ‘KS 370’ after 72 h culture increased significantly by increasing the ionic strength of the solution. Root concentrations of P, K, Ca, Mg, and Fe increased as the ionic strength of the solution increased in both cultivars. The N concentrations of roots in either ‘KS 370’ or ‘KS 352’ had positive correlations with an increasing ionic strength of the solution, although they were constantly greater in ‘KS 370’ than in ‘KS 352’. The greatest fresh weight was obtained when the plants were cultured in a half strength solution. Whereas dry weight decreased in all treatments as the ionic strength of the solution decreased. These findings show that increased ion absorption affected plant dry weight. The obtained findings provide fundamental information for the closed hydroponic system of phalaenopsis cultivation.  相似文献   
106.
A survey was undertaken to determine the wastes/residues generated by the food processing industry in the state of Iowa by sending a questionnaire to food processors with more than ten employees. Food processors were asked to provide a company profile, information about food waste/residue generated, and information about current disposal methods. Samples of wastes/residues were obtained from food processors willing to provide them, and proximate analysis was done. The overall response rate was 82.2 percent or 365 respondents out of 444 questioned. Companies under different category of standard industrial code (SIC) could produce similar wastes/residues that were classified in the same waste/residue streams. Within the meat and seafood category, the majority (87.7 percent) of the wastes/residues were generated by SIC codes 2077 (animal, marine fats and oils) and 2015 (poultry slaughtering, dressing, and processing). Among the waste management practices reported, excluding “other,” land application accounted for 14.0 percent of the waste stream, followed by rendering with 11.4 percent, landfill with 6.7 percent, sewage on-site with 5.0 percent and animal feed production off-site with 4.3 percent. Other waste management practices (combinations of major practices or others not clearly defined) account for 55.1 percent of the allocation of the waste stream.  相似文献   
107.
Lotus-leaf-like nanofibrous surfaces were prepared by electrospinning hydrophobic poly(vinylidene fluoride) (PVDF) from a mixed solvent of N,N-dimethylformamide (DMF) and acetone. PVDF fibrous mats with a bead-on-string morphology were generated because the nonpolar acetone decresed the viscosity of the PVDF solution and promoted the evaporation of the solution during electrospinning process. The morphology of the nanofibirous surface was examined by scanning electron microscopy. Micron-sized beads were introduced to the electrospun PVDF mats, resulting in enhanced hydrophobicity of the electrospun mats. The addition of a small amount (0.05 vol%) of acetic acid to the polymer solution effectively improved the bead-on-string morphology of the electrospun mats, and led to a higher water contact angle (WCA). The electrospun PVDF fibrous mat showed a maximum WCA of 148.5° due to the appropriate surface roughness.  相似文献   
108.
The permeability defined by Darcy’s law indicates the degree of ability that a fluid can flow through nonwoven media under a differential pressure in laminar flow. The permeability generally indicates the specific permeability or absolute permeability. On the other hand, if the fluid is water, the permeability indicates the hydraulic conductivity or permeability coefficient. The permeability is one of the important properties for nonwoven media and a prediction of the permeability acts as a bridge between the manufacturing technology and performance requirements. Because capillary channel theory aims to make the flow of fluid easier and more understandable, many models are based on capillary channel theory. On the other hand, the theory has a limitation in that it is unsuitable for high porosity media. In this study, a very thin downstream layer, which was suggested by Lifshutz [9], was introduced to derive a prediction model of hydraulic permeability. Needle-punched and spunbonded nonwoven fabrics with various basis weights were used in the cross-plain water permeability test. From this ‘thin layer’ model, reasonable agreement between the predicted and experimental results was obtained.  相似文献   
109.
Small starch particles were prepared by hydrolyzing waxy rice starch using α‐amylase and then ultrasonicating in ethanol. Differential scanning calorimetry (DSC) revealed that a mild hydrolysis for 3 hr increased the melting enthalpy of the starch, which might indicate that the hydrolysis was selective in the amorphous regions. Later, at 6–24 hr, the hydrolysis rate was reduced, with gradual decreases in DSC melting enthalpy, indicating that the crystalline regions were eroded simultaneously. X‐ray diffraction patterns revealed the same trend as the DSC results. Average diameter of starch granules or particles was decreased dramatically in both volume‐ and number‐based measurements (5.94→1.64 μm, and 0.45→0.18 μm, respectively) during the early stage of rapid hydrolysis (up to 3 hr). Native waxy rice starch exhibited a particle size distribution with a major peak at 5.6 μm. After hydrolysis for 3 hr, the volume distribution of starch granules changed to two major size peaks at 0.5 and 3.6 μm. The starch fragment of 0.5 μm was assumed to consist of crystalline blocklets. With excessive hydrolysis (24 hr) or ultrasonication, however, starch particle diameter was increased, indicating that the particles might be swollen or aggregated into clusters.  相似文献   
110.
BackgroundHepatocellular carcinoma is the most common primary hepatic malignancy in humans and dogs. Several differentially expressed molecules have been studied and reported in human hepatocellular carcinoma and non-neoplastic liver lesions. However, studies on the features of canine hepatocellular carcinoma are limited, especially related to the differential characteristics of neoplastic and non-neoplastic lesions.ObjectivesThe study''s objective was 1) to examine and evaluate the expression of arginase-1, P-glycoprotein, and cytokeratin 19 in canine liver tissues and 2) to investigate the differential features of hepatocellular carcinomas, liver tissue with non-neoplastic lesions, and paracancerous liver tissues in dogs.MethodsThe expression levels of three markers underwent immunohistochemical analysis in 40 non-neoplastic liver tissues, 32 hepatocellular carcinoma tissues, and 11 paracancerous liver tissues. Scoring of each marker was performed semi-quantitatively.ResultsArginase-1 and P-glycoprotein were significantly downregulated in hepatocellular carcinoma, compared with hepatic tissues with non-neoplastic diseases (p < 0.001). Expression levels of arginase-1 and P-glycoprotein were also significantly lower in hepatocellular carcinoma than in paracancerous liver tissues (arginase-1, p = 0.0195; P-glycoprotein, p = 0.047). Few cytokeratin 19-positive hepatocytes were detected and only in one hepatocellular carcinoma and one cirrhotic liver sample.ConclusionsThe results of this study suggest that downregulation of arginase-1 and P-glycoprotein is a feature of canine hepatocellular carcinoma; thus, those markers are potential candidates for use in differentiating hepatocellular carcinomas from non-neoplastic liver lesions in dogs.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号